KR102070317B1 - Lead-free solder composition and method for maunfacturing thereof - Google Patents

Abstract

It relates to a lead-free solder alloy composition and a method for manufacturing the same, a solder comprising at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag and Sn-Bi-In alloy; And it can provide a lead-free solder alloy composition comprising an additive comprising tungsten (W) metal nano powder.
According to one embodiment of the invention, there is no toxicity, by solving the environmental problems caused by the toxicity of lead (Pb), it is possible to minimize the impact of harmful metal elements such as lead to the environment, and excellent mechanical properties It is possible to provide a lead-free solder alloy composition having and a method of manufacturing the same.

Description

LEAD-FREE SOLDER COMPOSITION AND METHOD FOR MAUNFACTURING THEREOF

The present invention relates to a lead-free solder alloy composition and a method for manufacturing the same, and more particularly, to the environmental problem caused by the toxicity of lead (Pb), which is non-toxic, by the harmful metal elements such as lead to the environment It can be minimized, and relates to a lead-free solder alloy composition having excellent toughness and solderability and a method for manufacturing the same.

In general, Sn-Pb-based solder has been used as the most effective bonding material for electronic devices for a long time, especially as a bonding material for mounting small electronic components such as semiconductor chips and resistance chips on printed circuit boards. It is used.

However, when disposing of electronic devices using flexible solder, lead (Pb) contained in the solder is eluted by acid rain, which contaminates the groundwater, and if it is absorbed by the human body, it causes environmental pollution such as deterioration of intelligence and reproductive function. It is pointed out as a substance. Among them, the lead (Pb) contained in the flexible solder is strictly limited, Sn-Pb solder is replaced by lead-free solder.

For this reason, various attempts have recently been made to develop environmentally friendly lead-free solder compositions by regulating or excluding lead in the manufacture of solder alloys.

A technique related to such a lead-free solder has been proposed in Patent No. 00209241 and Patent No. 10-2007-0067860.

In the lead-free solder composition of the prior art 1, which is registered in Korean Patent No. 00209241, in the lead-free solder composition composed of tin (Sn), silver (Ag), bismuth (Bi), and indium (In), the tin (Sn) is 82 ~ 93wt%, silver (Ag) is 2wt%, bismuth (Bi) is 3-10wt%, indium (In) is prepared by mixing 2-6wt%. However, the solder for implementing the lead-free solder composition according to the prior art 1 has a problem that the ductility is reduced with the increase of the bismuth (Bi) content causing brittleness.

The lead-free solder composition of the prior art 2, which is Patent No. 10-2007-0067860, relates to a low-melting point lead-free solder and a method for manufacturing the same. Include. However, since the prior art 2 includes an alloy plating layer for manufacturing a low melting point lead-free solder, the process is complicated, and thus, there is a problem in that it is generally not applicable to the industry due to the problem of lowering productivity and increasing process cost.

On the other hand, in research and development of lead-free solder containing elements such as Sn, Ag, Bi, Cu, In, Zn, and the like, in particular, interest in a composition containing Sn, Ag, Cu has increased.

However, the above-mentioned lead-free solders each have disadvantages. For example, Zn is sensitive to oxidation and consequent decrease in solderability. Sn-Cu solders are inexpensive but poor in wettability, and are easy to form Ag ₃ Sn, a coarse acicular compound, in solders containing Ag, deteriorating solderability and lowering strength.

For lead-free solders containing silver or copper, Sn-0.7% Cu, Sn-3.5% Ag, 96.5wt% Sn-3.0wt% Ag-0.5wt% Cu alloys have the best wettability and reliability among lead-free solders, but melting point It is the biggest disadvantage that about 30-40 degreeC is higher than this conventional typical Sn-37Pb flexible solder (melting point: 183 degreeC). In addition, these microstructures include a dendritic phase and a process phase composed of beta-Sn, Ag ₃ Sn, Cu ₆ Sn ₅ , and when Ag ₃ Sn and Cu ₆ Sn ₅ are too large or too large, the Sn-based solder The brittleness increases and the strength decreases.

Therefore, the soldering of electronic products causes damage to semiconductors or electronic components due to thermal damage, and has a disadvantage in that current soldering processes cannot be applied as they are due to high soldering temperatures. In the case of the Sn-In system, In-49.1% Sn is the process composition and the process temperature is very low at 117, but the disadvantage is that the price is high. In conclusion, the development of lead-free solders requires minimizing the aforementioned drawbacks.

Currently, Sn-Bi-based lead-free solder most commonly used among low-melting point lead-free solders has a process composition of Sn-58Bi and a process temperature of about 139, which is a low temperature solder having a relatively low process temperature. Here, when Bi is added, the melting point is lowered, and the wettability tends to be somewhat improved. However, in this case, due to the relatively high Bi content, there is a problem that the ductility is lowered, causing brittleness.

As a method for this, it is necessary to include the particle refining material in the solder composition, and such materials include ceramic powders such as titanium oxide (TiO ₂ ), aluminum nitride (AlN), yttrium oxide (Y ₂ O ₃ ), and the like. Such ceramic powder material has the advantage of miniaturizing the particles and stable at high temperature to strengthen the solder.

However, the ceramic powder has poor wettability, and thus has a disadvantage in that the powder is agglomerated in the manufacture of the ceramic nanocomposite solder alloy or is not well mixed with the Sn metal as a base.

In addition, spherical nanopowders have a weaker mechanical bond between Sn metal and nanopowders than non-spherical nanopowders.

In order to solve the problem of the spherical ceramic nano-powder as described above, there is a method using a metal nano-powder such as aluminum (Al), nickel (Ni), silver (Ag), copper (Cu), tungsten (W) and the like. .

In addition, by coating a metal on the surface of the nano-powder in the manufacture of the solder composition using the nano-powder as described above, the wettability is further improved to prevent agglomeration of the powder during the production of the composite solder alloy, metal containing a non-spherical nano-powder There is a need for nano-composite lead-free solders that are prepared by producing nanopowders, which are well mixed with the base Sn metal to reinforce the Sn base of the solder, and also have excellent ductility and toughness.

(Patent Document 1) KR 10-0209241 B1

(Patent Document 2) KR 10-0797161 B1

The present invention relates to a lead-free solder alloy composition and a method for manufacturing the same, and more particularly, to the environmental problem caused by the toxicity of lead (Pb), which is non-toxic, by the harmful metal elements such as lead to the environment It is possible to minimize, and to provide a lead-free solder alloy composition having excellent toughness and solderability and a method of manufacturing the same.

In one embodiment of the present invention, a solder including at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag and Sn-Bi-In alloy; And it provides a lead-free solder alloy composition comprising an additive comprising a nano powder.

It may further include a coating layer of a metal material located on at least a portion of the surface of the nanopowder.

The Sn-Bi alloy is in weight percent, Bi: 35 to 73%, balance Sn and other inevitable impurities, the Sn-In alloy in weight%, In: 5.0 to 70%, balance Sn and other unavoidable impurities The Sn-Bi-Ag alloy is composed of weight percent, Bi: 35 to 75, Ag: 0.1 to 20, residual Sn and other unavoidable impurities, and the In-Ag alloy is weight percent, Ag: 30% or less, balance In and other inevitable impurities, and the Sn-Bi-In alloy may be composed of weight%, Bi: 15 to 65%, In: 5.0 to 75%, balance Sn and other unavoidable impurities. have.

Irregular uneven structures may be formed on the surface of the nanopowder by plasma etching and sputtering.

The nano powder may be a nano powder selected from the group consisting of W, Sr, Cu, Ni, Ag, Au, Fe, Co, Ti, Pt, Mo, Si, Pd and Cr.

The average particle size of the nanopowder may be 1 to 500 nm.

The metal coated on the surface of the nanopowder is at least one metal selected from the group consisting of In, Sn, Sb, Bi, Zn, Cu, Ag, Au, Ni, Pt, Pd, Fe, Co, Ti, Cr, and Mn. Can be.

The present invention also, in order to achieve the above object, nano powder manufacturing step of manufacturing a nano powder, the additive surface treatment step of forming an irregular concave-convex structure on the surface by the nano powder plasma etching and sputtering treatment (optional), At least one element selected from the group consisting of Bi and In, the nano-powder comprises a metal-coated (optional) additive (0.01 to 1.0% by weight), the Bi content is 35 to 65 weight %, The content of In is 5 to 30% by weight, the lead-free solder alloy composition for producing a solder alloy composition of 0.01 to 1.0% by weight of the additives by mixing the solder alloy with the balance of Sn and the nano-powder It provides a low melting lead-free solder alloy composition comprising the step.

In another embodiment of the present invention, preparing an additive including a nano powder; Melting a solder containing at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag, and Sn-Bi-In alloy; It provides a lead-free solder alloy composition comprising a; and mixing the additives and the molten solder to prepare a composition by stirring.

The lead-free solder alloy composition manufacturing step is a lead-free solder alloy melt manufacturing step of producing an alloy melt by mixing the solder alloy powder and the nano powder additive; And a bulk lead-free solder alloy composition manufacturing step of preparing the bulk composition by stirring the lead-free solder alloy melt.

The lead-free solder alloy composition manufacturing step may be performed by adding the nano-powder additive to the solder paste prepared by mixing the solder alloy powder and flux.

After preparing the composition, the step of passing the stirred composition through the through-hole processing in the form of a solder ball; may further include a.

According to the present invention, there is no toxicity, and by solving environmental problems caused by the toxicity of lead (Pb), it is possible to minimize the impact of harmful metal elements such as lead to the environment, lead-free solder having excellent toughness and solderability There is an effect that can provide an alloy composition and its preparation method.

1 is a block diagram showing a method of manufacturing a lead-free solder alloy composition according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing an apparatus including a knife impeller and a mixing vessel for performing a method of preparing a lead-free solder alloy composition according to an embodiment of the present invention.
Figure 3 is a schematic diagram showing a stainless steel propeller for performing a method of manufacturing a lead-free solder alloy composition according to an embodiment of the present invention.
4 is a view showing the effect of the nano-powder without the metal coating layer is formed and the powder with the metal coating layer formed on the internal dispersion of the solder.
Figure 5 is a photograph showing the state before and after coating the metal on the nano-powder in the method for producing a lead-free solder alloy composition according to an embodiment of the present invention.
Figure 6 is a graph showing the stirring conditions according to the stirring time and propeller rotation speed of the lead-free solder alloy melt in the method for producing a lead-free solder alloy composition according to an embodiment of the present invention.
Figure 7 is a photograph showing the powder before and after the sputtering and plasma etching of the nano-powder in the step of processing the surface of the additive according to an embodiment of the present invention.
8 is an FE-SEM photograph of a lead-free solder alloy composition to which nanoparticles are added according to an embodiment of the present invention.
Figure 9 is a graph measuring the tensile strength and elongation of the lead-free solder alloy composition to which the nano-powder is added according to an embodiment of the present invention.

The terms or words used in the present specification and claims are meant to be consistent with the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of the term in order to best explain his invention. It should be interpreted as and concepts.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only one embodiment is to make the disclosure of the present invention complete, the scope of the invention to those skilled in the art It is provided to inform you completely.

In one embodiment of the present invention, a solder including at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag and Sn-Bi-In alloy; And it provides a lead-free solder alloy composition comprising an additive comprising a nano powder.

It may further include a coating layer of a metal material located on at least a portion of the surface of the nanopowder.

The Sn-Bi alloy is in weight percent, Bi: 35 to 73%, balance Sn and other inevitable impurities, the Sn-In alloy in weight%, In: 5.0 to 70%, balance Sn and other unavoidable impurities The Sn-Bi-Ag alloy is composed of weight percent, Bi: 35 to 75%, Ag: 0.1 to 20%, residual Sn and other unavoidable impurities, and the In-Ag alloy is weight percent, Ag: 30% or less, balance In and other inevitable impurities, and the Sn-Bi-In alloy is in weight percent, Bi: 15 to 65%, In: 5.0 to 75%, balance Sn and other unavoidable impurities Can be.

In addition, another embodiment of the present invention, preparing an additive comprising a nano powder; Melting a solder containing at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag, and Sn-Bi-In alloy; It provides a lead-free solder alloy composition comprising a; and mixing the additives and the molten solder to prepare a composition by stirring.

That is, the lead-free solder alloy composition according to the present invention includes an additive in which the metal is coated on the nanopowder or the nanopowder in the lead-free solder alloy including Sn, Bi, and In elements, so that the nanoparticle additive is a matrix of the solder alloy and the metal. Evenly refine the liver compound to improve the ductility and toughness of the alloy. In addition, by preventing the cracks and cavities of the solder that can occur due to the large intermetallic compound of the particle size to prevent damage to the solder joints, there is a feature that increases the reliability and life of the solder joints.

Furthermore, the lead-free solder alloy composition according to the present invention includes additives coated with metal on the nanopowder, thereby having higher ductility and toughness than conventional lead-free solder alloys to which no additives are added, and thus have a high resistance to impact. In addition, flow and wettability may be improved, thereby preventing the defect of the soldering part.

Irregular uneven structures may be formed on the surface of the nanopowder by plasma etching and sputtering. That is, irregular irregularities formed by plasma etching and sputtering treatment of the surface of the nanopowder are incorporated into the hollow holes or recesses of the nanopowder surface by the anchor effect, resulting in increased mechanical bonding force. By doing so, there is an effect of improving the ductility and toughness of the alloy. This anchor effect can be further improved by plasma etching and sputtering the nanopowder surface after coating the nanopowder.

In addition, the lead-free solder alloy composition may further improve the performance of the lead-free solder alloy composition such as ductility and toughness by using an alloy in the above-described composition range.

The nano powder may be a nano powder selected from the group consisting of W, Sr, Cu, Ni, Ag, Au, Fe, Co, Ti, Pt, Mo, Si, Pd and Cr.

In addition, the nano-powder additive is prepared using a nano-powder having an average particle size of 1 to 500nm, it is possible to more easily prepare a lead-free solder alloy composition excellent in toughness and ductility.

The metal coated on the surface of the nanopowder is at least one selected from the group consisting of In, Sn, Sb, Bi, Zn, Cu, Ag, Au, Ni, Pt, Pd, Fe, Co, Ti, Cr, and Mn. Metal may be used, and the metal coated on the surface of the nanopowder may be formed by metal vapor deposition or electroless plating.

In addition, by plasma etching and sputtering on the surface of the metal-coated nanopowder, irregular concave-convex structures are formed on the surface of the powder, and this structure is incorporated into the hollow holes or recesses of the Sn solder by the anchor effect. As a result, the mechanical bonding force is increased, thereby improving the toughness of the alloy. This anchor effect can be further improved by plasma etching and sputtering the nanopowder surface after coating the nanopowder.

The additives improve the properties of the solder microstructure and refine the intermetallic compound (IMC) size in the solder to improve the ductility and toughness of the solder.

8 is an FE-SEM photograph of a lead-free solder alloy composition to which nanoparticles are added according to an embodiment of the present invention. FIG. 9 is a graph illustrating tensile strength and elongation of a lead-free solder alloy composition to which nanoparticles are added according to an embodiment of the present invention.

Referring to these drawings, the performance of the lead-free solder alloy composition according to the present invention will be described. Sn-58% Bi lead-free solder to which at least one nano-powder additive selected from the nano-powders is not added, and W is used as the nano-powder additive. Comparing the average β-Sn dendrite size of the added Sn-58% Bi lead-free solder, the average β-Sn dendrite of the Sn-58% Bi solder without the nanopowder was measured to be approximately 6.04 μm, but the nanopowder was 0.2 The average β-Sn dendrite of the wt added solder was 3.57μm, W nano powder coated with metal Au 0.2wt% The average β-Sn dendrite of the added solder was 2.26μm, 0.2 wt% W nano powder coated with metal Au Plasma etching of the added solder showed 2.09 μm.

Comparing the tensile strength with or without the nanopowder additive, the tensile strength of Sn-58% Bi solder without the nanopowder added was measured as 64.96 MPa. In order to manufacture the lead-free solder alloy composition to which the nano-powder was added, a tensile test was performed after performing plasma etching under all conditions. The tensile strength of the nano-powder W added 0.2% to the Sn-58% Bi solder was 72.12 MPa, and the tensile strength of the metal to the nano-powder W was 71.56 MPa.

When comparing the elongation according to the presence or absence of the nanopowder additive, the elongation of Sn-58% Bi solder without the nanopowder added was measured to be 13.45%. In order to manufacture the lead-free solder alloy composition to which the nano-powder was added, a tensile test was performed after performing plasma etching under all conditions. When 0.2% of the nano-powder W was added to the Sn-58% Bi solder, the elongation was 18.82%, and the elongation when the metal was coated on the nano-powder W was 23.33%.

That is, the grain size of the solder is refined due to the addition of the nanopowder, and strength and ductility are increased. In addition, the elongation of the lead-free solder alloy was increased due to the plasma etching and the metal coating. In general, when the grain size of the metal is refined, the yield strength and tensile strength increase by the Hall-Petch equation as follows.

σy: Reinforced yield strength

σ0: Yield strength of the material

K: constant

d: Particle diameter

In the case of the nanocomposite lead-free solder to which the nanopowder according to the present invention is added, the nanopowder, which is much higher than the solder melting point, is present as a fine nano-sized solid when it is melted and solidified during soldering. The added powder acts as a solid nucleation site (seed) upon coagulation. As a result, the added nanopowders provide a greater number of nucleation sites, allowing solid crystals to be produced therein, resulting in finer grains than lead-free solder without the addition of nanopowder additives. In addition, the nano-powder inhibits the growth of the intermetallic compound in the solder, thereby miniaturizing the intermetallic compound, thereby contributing to the solder having more improved properties.

The lead-free solder alloy composition according to the present invention may include the nano powder additive as 0.01 to 1.0wt%. When content of the said nanopowder is less than 0.01 wt%, the improvement of solderability and strength hardly show. On the other hand, when added in excess of 1.0wt%, soldering property may be degraded and dewetting, which is a poor wetting, may occur.

In the following, the configuration and conditions of the solder composition in the present invention are shown in Table 1.

ingredient content
Lead free solder Sn-Bi Sn- (35 ~ 60)% Bi Sn-Bi-In Sn- (35 ~ 60)% Bi- (5 ~ 30)% In additive W

In order to improve performance for realizing the optimum strength and solderability (solderability) of the lead-free solder alloy composition according to the present invention, it is necessary to make the components of the solder to which the nanopowder additive is added to the optimum composition.

Lead-free solder alloy compositions according to the present invention can be used as the solder material. Specifically, it may be used for soldering pastes, solder balls, solder bars, solder wires, and the like, and electronic products using the same. Modern electronics are becoming smaller and smaller to meet the needs of high integration, low power or portability, size, operating voltage and so on. One serious issue here is the wettability and toughness of the soldering portion of the electronic device. In order to improve this, there is an increasing demand for a solder composed of improved wettability and micronized intermetallic compound, and other lead-free solder alloy compositions according to the present invention can be effectively used to remedy these disadvantages.

1 is a block diagram showing a method of manufacturing a lead-free solder alloy composition according to an embodiment of the present invention, Figure 2 is a knife for performing a method of manufacturing a lead-free solder alloy composition according to an embodiment of the present invention A schematic diagram showing an apparatus including an impeller and a mixing vessel is shown, and FIG. 3 illustrates a stainless steel propeller for carrying out a method of preparing a lead-free solder alloy composition according to an embodiment of the present invention. The schematic shown is shown.

4 is a view showing the effect of the nano-powder without the metal coating layer is formed and the powder formed with the metal coating layer on the internal dispersion of the solder, Figure 5 is a lead-free solder alloy according to an embodiment of the present invention In the manufacturing method of the composition is a photograph showing the appearance before and after coating the metal on the nano-powder.

Figure 6 is a graph showing the stirring conditions according to the stirring time and propeller rotation speed of the lead-free solder alloy melt in the method for producing a lead-free solder alloy composition according to an embodiment of the present invention, Figure 7 shows one embodiment of the present invention In the step of processing the surface of the additive according to the example is a photograph showing the powder before and after the sputtering and plasma etching of the nanopowder.

Referring to these drawings, the method for producing a lead-free solder alloy composition of the present invention, preparing an additive comprising a nano powder; Melting a solder containing at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag, and Sn-Bi-In alloy; It may be a lead-free solder alloy composition manufacturing method comprising a; and mixing the additives and the molten solder to prepare a composition by stirring.

In addition, the method for producing a lead-free solder alloy composition of the present invention, the nano powder manufacturing step of preparing a nano powder by grinding the powder, nano powder additive manufacturing step of manufacturing an additive by coating a metal on the surface of the nano powder, the nano powder An additive surface treatment step of forming an irregular concave-convex structure on the surface by plasma etching and sputtering the additive, by mixing the above-described solder alloy and the nano powder additive to prepare a solder alloy composition having a content of 0.01 to 1.0% by weight of the additive It may be configured to include a lead-free solder alloy composition manufacturing step.

Here, the nano-powder may be a nano powder selected from the group consisting of W, Sr, Cu, Ni, Ag, Au, Fe, Co, Ti, Pt, Mo, Si, Pd and Cr.
Coating at least a portion of the surface of the nanopowder with a metal material; may be performed by a method of coating for 70 to 300 seconds at a current of 20 to 60 mA using a sputter coater.

The plasma etching uses 70-95% CF ₄ + 5-30% O ₂ gas, is etched for about 30-180 minutes at a vacuum degree of 10 ~ 30mTorr, and also sputtering is performed at room temperature for about 50-300 seconds It can be sputtered with 10 to 50 mA current at 0.01 mbar to 1 mbar vacuum.

The nanopowder manufacturing step may perform grinding and dispersing of the nanopowder by using a grinding device including a knife impeller rotating at a high speed and a mixing vessel capable of rotating horizontally and vertically. have.

Specifically, the grinding apparatus 200 is a main body 210 in which a control circuit (not shown) of the apparatus, a switch 212, an internal display unit 213, and the like are formed, and a direction perpendicular to the main body 210. It is configured to include a mixing vessel 220 connected by a connecting portion 211 to be rotatably connected to.

The mixing vessel 220 is composed of an upper housing 221 rotating and mixing the inner grinding material in the vertical direction and a lower housing 222 rotating and mixing the inner grinding material in the horizontal direction. The high speed rotating knife impeller (not shown) may be configured to be installed in the lower housing 222.

The rotation speed of the knife impeller is preferably greater than the rotation speed of the mixing vessel 220. Specifically, the knife impeller rotates at 3,000 to 14,000 rpm, and the mixing is performed. The mixing vessel 220 may be pulverized and dispersed by dispersing the nanopowder by rotating at 10 to 30 rpm.

The lead-free solder alloy composition manufacturing step (S130), for example, includes at least one element selected from the group consisting of Bi, In and Sn, and comprises the nano-powder in 0.01 to 1.0% by weight, The content of Bi is 35 to 65% by weight, the content of In is 5 to 30% by weight, and the lead-free solder alloy melt manufacturing step of preparing an alloy melt by mixing the solder alloy powder with the balance Sn and the nano powder additives And a bulk lead-free solder alloy composition manufacturing step of preparing the bulk-type composition by stirring the lead-free solder alloy melt, for example, for uniform mixing of the lead-free solder, for example, at a temperature of 200 to 300 ° C. It can be carried out in an electric furnace.

The bulk lead-free solder alloy composition manufacturing step may be performed by stirring the lead-free solder alloy melt at 100 ~ 500rpm using a stainless steel propeller 320 for uniform mixing of the lead-free solder and nano powder additives. Here, the stainless steel propeller 320 is a four-shaped propeller of a rectangular shape that is used as one stirring propeller mechanism 300 by being coupled to the propeller shaft 310 elongated as a plate shape having a thickness thinner than the diameter value of the shaft. It can be produced as.

The lead-free solder alloy composition manufacturing step (S130) comprises at least one element selected from the group consisting of Bi, In, the balance of the solder alloy, Sn, for example, Sn-Bi first alloy, Sn -In the second alloy and Sn-Bi-In third alloy may be further prepared by grinding each of the at least one solder alloy selected from the group consisting of, but when using a commercially available solder powder grinding The process may be omitted, and the soldering flux may be prepared and mixed.

The nano powder manufacturing step (S100) of preparing the nano powder by pulverizing the powder is a step of pulverizing and dispersing the nano powder to prevent agglomeration of the nano powder added to the nanocomposite lead-free solder alloy preparation. The grinding apparatus 200 can be used to grind and disperse.

In this case, the knife impeller rotates at 3,000 to 14,000 rpm, and the mixing vessel 220 rotates at 10 to 30 rpm to pulverize and disperse the nanopowder. In addition, the knife impeller rotation speed should be greater than the rotation speed of the mixing vessel 220 to obtain good dispersion characteristics. If the rotating speed of the mixing vessel 220 is greater than the rotating speed of the knife impeller, the powder will stick to the inner wall of the mixing vessel 220 by centrifugal force to cause a knife impeller. The contact with the (knife impeller) is worsened and a good grinding and dispersing effect is not obtained. In addition, since a lot of energy is consumed to rotate the mixing vessel 220, which is bulkier than the knife impeller, the grinding and dispersing efficiency is lowered.

The nano powder additive manufacturing step (S110) is a step of coating the nano powder to improve the wettability and spreadability, the nano powder may be coated by a metal vapor deposition method or an electroless plating method. At this time, the metal to be coated on the nano-powder is In, Sn, Sb, Bi, Zn, Cu, Ag, Au, Ni, Pt, Pd, Fe, Co, Ti, Cr, and Mn, the metal coating of the powder surface Improved wettability of silver powder to prevent agglomeration of powder when manufacturing nanocomposite solder alloy, and it is well mixed with the base Sn metal to strengthen the Sn base of solder, and can produce nanocomposite lead-free solder having excellent wettability. There is this.

The lead-free solder alloy composition manufacturing step (S130) is a step of manufacturing a molten solder in a heating furnace of 200 ~ 300 ℃ temperature, to be carried out by maintaining the method for 10 to 30 minutes in a non-oxidizing atmosphere such as air or nitrogen atmosphere, vacuum Can be.

The lead-free solder alloy melt manufacturing step is to add a nano powder additive in the molten lead-free solder alloy, the nano powder is W, Sr, Cu, Ni, Ag, Au, Fe, Co, Ti, Pt, Mo, Nano powder selected from the group consisting of Si, Pd and Cr can be used, the average diameter is 1 ~ 500nm, may be added in the range of 0.01 ~ 1.0wt%.

The bulk lead-free solder alloy composition manufacturing step is to disperse and mix the nanopowder in the molten solder, using the stainless steel propeller 320 at a temperature of 200 ~ 300 ℃ 10 to 50 minutes (more specifically 10 30 minutes), and may be performed by dispersing the nanopowder in the molten solder by rotating at about 100 to 500 rpm during stirring. Here, the stainless steel propeller 320 is very low reactivity with the molten solder is suitable as a stirring propeller.

In addition, if the rotational speed of the stainless steel propeller 320 is less than 100 rpm during stirring, the stirring becomes insufficient, so that the nano powder is easily entangled and the dispersion effect is not large. Since the oxidation of the stainless steel propeller 320 may be intensified, the rotational speed of 100 ~ 500 rpm is appropriate.

On the other hand, the lead-free solder alloy composition manufacturing step (S130) may be performed by adding the nanopowder additive to the solder paste prepared by mixing the solder alloy powder and flux, the flux and the nanopowder to the solder alloy powder It can be done by mixing the additives simultaneously to produce a solder paste.

In addition, after the step of preparing the composition, the step of processing in the form of a solder ball by passing the stirred composition through a through hole; may further include.

< Example  1> Nano Composite Lead Free Solder  Preparation and Microstructure Properties of the Composition

The vessel was rotated at 30 rpm and the impeller was rotated at 4500 rpm to grind the W powder for 10 minutes. Through this, W nanopowder was prepared to include an amorphous nanopowder having a purity of 99.9% and a size of 100 nm or less.

Subsequently, the additive was prepared by coating Au metal on the surface of the nano powder using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 300 seconds with a current of about 30 mA. The thickness of the coated metal is about 500 mm 3.

Next, the additive surface was plasma etched and sputtered. 95% CF ₄ + 5% O ₂ gas was used for the plasma etching, and was etched for about 90 minutes at a vacuum of 40 mTorr.

The SnBi solder was melted for about 10 minutes in a 200 ° C. temperature electric furnace in an atmosphere and a nitrogen atmosphere. Subsequently, an additive coated with Au to the W nanopowder was added to the molten solder at 0.2% by weight of the total composition, and stirred at 300 rpm for 20 minutes using a stainless steel propeller having a rectangular 4-blade shape. Comparing the grains of the SnBi lead-free solder without addition of at least one nano powder additive selected from the nano powders and the SnBi lead-free solder with W added as a nano powder additive, the average of the Sn-58% Bi solder without the nano powder added The β-Sn dendrite was measured to be approximately 6.04 μm, but the average β-Sn dendrite was 3.57 μm and the average β-Sn of the 0.2 wt% solder of the metal Au-coated W nanopowder was 3.57 μm. The dendrite was 2.26 μm and 2.09 μm when plasma etching was applied to the solder containing 0.2 wt% of the W nanopowder coated with metal Au. 8 shows a FE-SEM photograph.

< Example  2> Nano Composite Lead Free Solder  Preparation of Alloys and Mechanical Properties of Alloys

The vessel was spun at 35 rpm and the impeller was spun at 4000 rpm to pulverize the powder for 10 minutes. Through this, W nanopowder was prepared to include an amorphous nanopowder having a purity of 99.9% and a size of 100 nm or less.

Subsequently, an additive was prepared by coating a metal on the surface of the nanopowder using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 300 seconds with a current of about 40 mA. The thickness of the coated metal is about 300 mm 3.

Next, the additive surface was plasma etched and sputtered. 70% CF ₄ + 30% O ₂ gas was used for the plasma etching, and was etched for about 90 minutes at a vacuum degree of 40 mTorr. SnBi and SnBiIn solders were melted for about 20 minutes in an air and nitrogen atmosphere 250 ° C. electric furnace. Subsequently, an additive coated with a metal on the W nanopowder was added to the molten solder, and stirred at 500 rpm for 15 minutes using a rectangular four-blade stainless steel propeller.

Tensile strength when no additive is added to the solder, when the additive composed of nano powder is added to the solder, when the nano powder additive with the coating layer formed on the surface is added to the solder, and when the additive is processed with the additive surface. And elongation can be confirmed through the graph of FIG.

Comparing the tensile strength with or without the nanopowder additive, the tensile strength of Sn-58% Bi solder without the nanopowder added was measured as 64.96 MPa. In order to manufacture the lead-free solder alloy composition to which the nano-powder was added, a tensile test was performed after performing plasma etching under all conditions. The tensile strength of the nano-powder W added 0.2% to the Sn-58% Bi solder was 72.12 MPa, and the tensile strength of the metal to the nano-powder W was 71.56 MPa.

When comparing the elongation according to the presence or absence of the nanopowder additive, the elongation of Sn-58% Bi solder without the nanopowder added was measured to be 13.45%. In order to manufacture the lead-free solder alloy composition to which the nano-powder was added, a tensile test was performed after performing plasma etching under all conditions. The elongation of 0.2% of the nano-powder W added to the Sn-58% Bi solder was 18.82%, and the elongation of the metal of the nano-powder W to 23.33%.

As a result, the particles of the SnBi and SnBiIn solder of the nanoparticles according to the present invention are made fine, and the strength and elongation are increased. Alloys with fine particles further interfere with dislocation transfer, increasing the mechanical properties of the alloy.

This phenomenon may have a similar effect when using oxide, nitride, carbide, boride nanoparticles of other elements in addition to the nanoparticles of the embodiment.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from these descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

Claims (14)

delete delete delete delete delete delete delete Preparing an additive comprising tungsten (W) metal nano powder having an average particle size of 1 to 500 nm;
Coating at least a portion of the nanopowder surface with a metal material;
Processing the surface of the additive by performing plasma etching;
Melting a solder containing at least one alloy selected from Sn-Bi alloy, Sn-In alloy, Sn-Bi-Ag, In-Ag, and Sn-Bi-In alloy; And
And mixing the additives with the molten solder and then stirring to prepare a composition.
Preparing an additive comprising the nano-powder ;, The method for producing the nano-powder to include an amorphous nano-powder by using a vessel rotating at 10 to 30rpm and an impeller rotating at 3000 to 14000rpm in the vessel Performed by
The plasma etching is etched for 30 to 180 minutes at 70 to 95% by volume CF ₄ and 5 to 30% by volume O ₂ gas atmosphere and 10 to 30 mTorr vacuum degree,
Step of preparing the composition is a method for producing a lead-free solder alloy composition for stirring for 10 to 50 minutes using a propeller rotating at 100 to 500rpm. delete delete delete The method of claim 8,
Coating at least a portion of the nanopowder surface with a metal material;
Method for producing a lead-free solder alloy composition that is carried out by the method of coating for 70 to 300 seconds at a current of 20 to 60mA using a sputter coater. delete delete

Images